1. Field of the Invention
This invention relates to polyurethane compositions, and more particularly, to polyurethane compositions which are resistant to swelling in oil and/or water. The invention also relates to a novel polyol composition useful to make the polyurethane composition.
2. Prior Art
Polyurethane resins have been prepared for a number of years by the reaction of organic polyols and other similar reactive compounds, diisocyanates and optionally chain extending agents. By the appropriate selection of precursor components, the physical characteristics of the cured polyurethane resins may be varied from soft elastomers to hard, even brittle, materials that may be soluble either in organic solvents or water. It is also known that with increased cross-linking of such polymers, generally by increasing the concentration of components having more than two functional groups, the softening point and modulus of such polymers are increased with a corresponding reduction in the elongation and swelling in solvents. Such modifications are discussed in Saunders and Frisch, Polyurethanes, Chemistry and Technology, Part I, pages 264 and 320, Interscience Pub. (1963).
Polyurethanes cross-linked by use of polyols having two or more hydroxyl groups are disclosed, for example, in U.S. Pat. Nos. 2,915,496; 3,012,987; 3,541,183; 3,792,003 and 3,933,725. No teaching can be found in any of these patents of substantially non-swelling polyurethane compositions. The term "substantially non-swelling" as herein used means, after immersion in oil or water at ambient temperature, e.g., 20.degree. C.-25.degree. C., and for a prolonged period of time, e.g., at least one week, a polyurethane sample will have a volume change of less than about 3%, preferably less than 1.0%.
Polyurethanes have also been prepared using halogen-containing polyether polyols to provide flame resistance to articles manufactured therefrom and are disclosed in many patents, including, for example U.S. Pat. Nos. 3,245,957; 3,252,922; 3,255,126; 3,260,687; 3,412,048 and 3,878,157 (also U.S. Pat. Nos. 3,879,329; 3,929,709; 3,956,221; 3,965,073 and 3,996,172 which are related to U.S. Pat. No. 3,878,157). Of these patents, U.S. Pat. Nos. 3,260,687; 3,412,048 and the family of patents of which U.S. Pat. No. 3,878,157 is parent, disclose compositions, from which the polyurethane is prepared, to contain polyols having three or more hydroxyl groups. None of these patents or other reference of which applicants are aware describe polyurethane resins prepared from halogen-containing polyether polyols, polyols having three or more hydroxyl groups, and polyisocyanates in the concentrations necessary to provide products which are substantially non-swelling in oil and water.
Polyurethanes substantially impermeable to solvents such as petrol and fuel oils are disclosed in U.S. Pat. No. 3,219,634. These polymers have been prepared by curing a mixture of a cross-linking agent and an isocyanate terminated polyurethane prepolymer based on polyepichlorohydrinpolyol. U.S. Pat. No. 3,219,634 teaches that polyurethanes can be made from prepolymers based on polyepichlorohydrinpolyol that has been mixed with non-halogen-containing polyetherpolyol (Col. 3, lines 30-37). Amounts of non-halogen-containing polyetherpolyol that can be used are however not disclosed. Examples 5 and 6 of U.S. Pat. No. 3,219,634, however, illustrate polyurethanes containing no less than 54 and 43 mole percent of polyepichlorohydrin polyol, respectively. Such polyurethanes, although resistant to fuel oils, are not resistant to softening on prolonged contact with water.